Crypt::PK::DSA(3) User Contributed Perl Documentation Crypt::PK::DSA(3)
NAME
Crypt::PK::DSA - Public key cryptography based on DSA
SYNOPSIS
### OO interface
my $message = 'hello world';
my $signer = Crypt::PK::DSA->new();
$signer->generate_key(30, 256);
my $signature = $signer->sign_message($message);
my $public_der = $signer->export_key_der('public');
my $verifier = Crypt::PK::DSA->new(\$public_der);
$verifier->verify_message($signature, $message) or die "ERROR";
my $ciphertext = $verifier->encrypt("secret message");
my $plaintext = $signer->decrypt($ciphertext);
my $private_der = $signer->export_key_der('private');
my $private_pem = $signer->export_key_pem('private');
my $public_pem = $verifier->export_key_pem('public');
DESCRIPTION
DSA is primarily a digital signature scheme. In this module, signing
and verification are the most common operations and therefore the
primary examples.
Legacy function-style wrappers still exist in code for backwards
compatibility, but they are intentionally undocumented.
METHODS
new
my $source = Crypt::PK::DSA->new();
$source->generate_key(20, 128);
my $public_der = $source->export_key_der('public');
my $pub = Crypt::PK::DSA->new(\$public_der);
my $private_pem = $source->export_key_pem('private', 'secret', 'AES-256-CBC');
my $priv = Crypt::PK::DSA->new(\$private_pem, 'secret');
Passing $filename or "\$buffer" to "new" is equivalent: both forms
immediately import the key material into the new object.
generate_key
Uses the bundled "chacha20" PRNG via libtomcrypt's "rng_make_prng".
Returns the object itself (for chaining).
$pk->generate_key($group_size, $modulus_size);
# $group_size ... [integer] size of the subgroup (q) in bytes; must satisfy: 15 < $group_size < 1024
# $modulus_size .. [integer] size of the prime (p) in bytes; must satisfy: ($modulus_size - $group_size) < 512
# $modulus_size must be >= $group_size
#
# The two-integer form uses Perl's usual numeric-to-integer coercion before
# the XS call. Callers should therefore pass exact integers; values like
# C<10.9> or C<"1e1"> will be coerced according to Perl's integer conversion.
### Common parameter pairs (group_size, modulus_size) => security level:
# generate_key(20, 128) => 80-bit security (1024-bit p, 160-bit q)
# generate_key(30, 256) => 120-bit security (2048-bit p, 240-bit q)
# generate_key(32, 256) => 128-bit security (2048-bit p, 256-bit q)
# generate_key(35, 384) => ~140-bit security (3072-bit p, 280-bit q)
# 140 bits => generate_key(35, 384)
# 160 bits => generate_key(40, 512)
### Sizes according section 4.2 of FIPS 186-4
# (L and N are the bit lengths of p and q respectively)
# L = 1024, N = 160 => generate_key(20, 128)
# L = 2048, N = 224 => generate_key(28, 256)
# L = 2048, N = 256 => generate_key(32, 256)
# L = 3072, N = 256 => generate_key(32, 384)
$pk->generate_key($param_hash)
# $param_hash is { p => $p, q => $q, g => $g }
# where $p, $q, $g are hex strings
$pk->generate_key(\$dsa_param)
# $dsa_param is the content of DER or PEM file with DSA params
# e.g. openssl dsaparam 2048
import_key
Loads private or public key in DER or PEM format.
my $source = Crypt::PK::DSA->new();
$source->generate_key(20, 128);
my $public_der = $source->export_key_der('public');
my $pub = Crypt::PK::DSA->new();
$pub->import_key(\$public_der);
my $private_pem = $source->export_key_pem('private', 'secret', 'AES-256-CBC');
my $priv = Crypt::PK::DSA->new();
$priv->import_key(\$private_pem, 'secret');
The same method also accepts filenames instead of buffers.
Loading private or public keys from a Perl HASH:
$pk->import_key($hashref);
# where $hashref is a key exported via key2hash
$pk->import_key({
p => "AAF839A764E04D80824B79FA1F0496C093...", #prime modulus
q => "D05C4CB45F29D353442F1FEC43A6BE2BE8...", #prime divisor
g => "847E8896D12C9BF18FE283AE7AD58ED7F3...", #generator of a subgroup of order q in GF(p)
x => "6C801901AC74E2DC714D75A9F6969483CF...", #private key, random 0 < x < q
y => "8F7604D77FA62C7539562458A63C7611B7...", #public key, where y = g^x mod p
});
Supported key formats:
o DSA public keys
-----BEGIN PUBLIC KEY-----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-----END PUBLIC KEY-----
o DSA private keys
-----BEGIN DSA PRIVATE KEY-----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-----END DSA PRIVATE KEY-----
o DSA private keys in password protected PEM format:
-----BEGIN DSA PRIVATE KEY-----
Proc-Type: 4,ENCRYPTED
DEK-Info: DES-CBC,227ADC3AA0299491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-----END DSA PRIVATE KEY-----
o SSH public DSA keys
ssh-dss AAAAB3NzaC1kc3MAAACBAKU8/avmk...4XOwuEssAVhmwA==
o SSH public DSA keys (RFC-4716 format)
---- BEGIN SSH2 PUBLIC KEY ----
Comment: "1024-bit DSA, converted from OpenSSH"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---- END SSH2 PUBLIC KEY ----
export_key_der
Returns the key as a binary DER-encoded string.
my $private_der = $pk->export_key_der('private');
#or
my $public_der = $pk->export_key_der('public');
export_key_pem
Returns the key as a PEM-encoded string (ASCII).
my $private_pem = $pk->export_key_pem('private');
#or
my $public_pem = $pk->export_key_pem('public');
#or
my $public_pem = $pk->export_key_pem('public_x509');
With parameter 'public' uses header and footer lines:
-----BEGIN DSA PUBLIC KEY------
-----END DSA PUBLIC KEY------
With parameter 'public_x509' uses header and footer lines:
-----BEGIN PUBLIC KEY------
-----END PUBLIC KEY------
Support for password protected PEM keys
my $private_pem = $pk->export_key_pem('private', $password);
#or
my $private_pem = $pk->export_key_pem('private', $password, $cipher);
# supported ciphers: 'DES-CBC'
# 'DES-EDE3-CBC'
# 'SEED-CBC'
# 'CAMELLIA-128-CBC'
# 'CAMELLIA-192-CBC'
# 'CAMELLIA-256-CBC'
# 'AES-128-CBC'
# 'AES-192-CBC'
# 'AES-256-CBC' (DEFAULT)
encrypt
Returns the ciphertext as a binary string.
DSA is usually used for signatures. This helper is available because
the underlying library exposes a DSA-based encryption primitive.
my $pk = Crypt::PK::DSA->new($pub_key_filename);
my $ct = $pk->encrypt($message);
#or
my $ct = $pk->encrypt($message, $hash_name);
# $hash_name .. [string] 'SHA1' (DEFAULT), 'SHA256' or any other hash supported by Crypt::Digest
decrypt
Returns the plaintext as a binary string.
my $pk = Crypt::PK::DSA->new($priv_key_filename);
my $pt = $pk->decrypt($ciphertext);
sign_message
Returns the signature as a binary string.
my $pk = Crypt::PK::DSA->new($priv_key_filename);
my $signature = $pk->sign_message($message);
#or
my $signature = $pk->sign_message($message, $hash_name);
# $hash_name .. [string] 'SHA1' (DEFAULT), 'SHA256' or any other hash supported by Crypt::Digest
verify_message
Returns 1 if the signature is valid, 0 otherwise.
my $pk = Crypt::PK::DSA->new($pub_key_filename);
my $valid = $pk->verify_message($signature, $message);
#or
my $valid = $pk->verify_message($signature, $message, $hash_name);
# $hash_name .. [string] 'SHA1' (DEFAULT), 'SHA256' or any other hash supported by Crypt::Digest
sign_hash
Returns the signature as a binary string.
my $pk = Crypt::PK::DSA->new($priv_key_filename);
my $signature = $pk->sign_hash($message_hash);
verify_hash
Returns 1 if the signature is valid, 0 otherwise.
my $pk = Crypt::PK::DSA->new($pub_key_filename);
my $valid = $pk->verify_hash($signature, $message_hash);
is_private
my $rv = $pk->is_private;
# 1 .. private key loaded
# 0 .. public key loaded
# undef .. no key loaded
size
my $size = $pk->size;
# returns key size (length of the prime p) in bytes or undef if key not loaded
size_q
my $size = $pk->size_q;
# returns length of the prime q in bytes or undef if key not loaded
key2hash
Returns a hashref with the key components, or "undef" if no key is
loaded.
my $hash = $pk->key2hash;
# returns hash like this (or undef if no key loaded):
{
type => 1, # integer: 1 .. private, 0 .. public
size => 256, # integer: key size in bytes
# all the rest are hex strings
p => "AAF839A764E04D80824B79FA1F0496C093...", #prime modulus
q => "D05C4CB45F29D353442F1FEC43A6BE2BE8...", #prime divisor
g => "847E8896D12C9BF18FE283AE7AD58ED7F3...", #generator of a subgroup of order q in GF(p)
x => "6C801901AC74E2DC714D75A9F6969483CF...", #private key, random 0 < x < q
y => "8F7604D77FA62C7539562458A63C7611B7...", #public key, where y = g^x mod p
}
OpenSSL interoperability
### let's have:
# DSA private key in PEM format - dsakey.priv.pem
# DSA public key in PEM format - dsakey.pub.pem
# data file to be signed - input.data
Sign by OpenSSL, verify by Crypt::PK::DSA
Create signature (from commandline):
openssl dgst -sha1 -sign dsakey.priv.pem -out input.sha1-dsa.sig input.data
Verify signature (Perl code):
use Crypt::PK::DSA;
use Crypt::Digest 'digest_file';
use Crypt::Misc 'read_rawfile';
my $pkdsa = Crypt::PK::DSA->new("dsakey.pub.pem");
my $signature = read_rawfile("input.sha1-dsa.sig");
my $valid = $pkdsa->verify_hash($signature, digest_file("SHA1", "input.data"));
print $valid ? "SUCCESS" : "FAILURE";
Sign by Crypt::PK::DSA, verify by OpenSSL
Create signature (Perl code):
use Crypt::PK::DSA;
use Crypt::Digest 'digest_file';
use Crypt::Misc 'write_rawfile';
my $pkdsa = Crypt::PK::DSA->new("dsakey.priv.pem");
my $signature = $pkdsa->sign_hash(digest_file("SHA1", "input.data"));
write_rawfile("input.sha1-dsa.sig", $signature);
Verify signature (from commandline):
openssl dgst -sha1 -verify dsakey.pub.pem -signature input.sha1-dsa.sig input.data
Keys generated by Crypt::PK::DSA
Generate keys (Perl code):
use Crypt::PK::DSA;
use Crypt::Misc 'write_rawfile';
my $pkdsa = Crypt::PK::DSA->new;
$pkdsa->generate_key(20, 128);
write_rawfile("dsakey.pub.der", $pkdsa->export_key_der('public'));
write_rawfile("dsakey.priv.der", $pkdsa->export_key_der('private'));
write_rawfile("dsakey.pub.pem", $pkdsa->export_key_pem('public_x509'));
write_rawfile("dsakey.priv.pem", $pkdsa->export_key_pem('private'));
write_rawfile("dsakey-passwd.priv.pem", $pkdsa->export_key_pem('private', 'secret'));
Use keys by OpenSSL:
openssl dsa -in dsakey.priv.der -text -inform der
openssl dsa -in dsakey.priv.pem -text
openssl dsa -in dsakey-passwd.priv.pem -text -inform pem -passin pass:secret
openssl dsa -in dsakey.pub.der -pubin -text -inform der
openssl dsa -in dsakey.pub.pem -pubin -text
Keys generated by OpenSSL
Generate keys:
openssl dsaparam -genkey -out dsakey.priv.pem 1024
openssl dsa -in dsakey.priv.pem -out dsakey.priv.der -outform der
openssl dsa -in dsakey.priv.pem -out dsakey.pub.pem -pubout
openssl dsa -in dsakey.priv.pem -out dsakey.pub.der -outform der -pubout
openssl dsa -in dsakey.priv.pem -passout pass:secret -des3 -out dsakey-passwd.priv.pem
Load keys (Perl code):
use Crypt::PK::DSA;
my $pkdsa = Crypt::PK::DSA->new;
$pkdsa->import_key("dsakey.pub.der");
$pkdsa->import_key("dsakey.priv.der");
$pkdsa->import_key("dsakey.pub.pem");
$pkdsa->import_key("dsakey.priv.pem");
$pkdsa->import_key("dsakey-passwd.priv.pem", "secret");
SEE ALSO
o <https://en.wikipedia.org/wiki/Digital_Signature_Algorithm>
perl v5.34.3 2026-05-11 Crypt::PK::DSA(3)
cryptx 0.89.0 - Generated Tue May 12 09:03:59 CDT 2026